1. Field of the Invention
The invention relates in general to a memory block transfer circuit, and more particularly to a bit alignment bit block transfer (Bitblt) circuit.
2. Description of the Related Art
In the modern times, the memory block transfer technology has existed. In an on screen display (OSD) device of a display, for example, the memory block transfer technology is applied to shift default graphic and menu information, stored in an off screen memory, to a frame buffer so that an OSD menu may be displayed on the display.
In the conventional memory block transfer technology, the minimum data quantity unit that may be operated is one byte. Thus, even if one bit of data in one byte is to be shifted, modified or accessed, the conventional memory block transfer technology has to perform the above-mentioned operation on the data of the whole byte. Consequently, the conventional memory block transfer technology occupies more memory transfer bandwidth.
In addition, in the occasion of applying the conventional memory block transfer technology to design a bit-based OSD module, one pixel is configured to correspond to at least 8 bits of OSD data such that the minimum image modifying and shifting unit of the bit-based OSD is one pixel because the minimum data quantity unit that can be operated is one byte in the conventional memory block transfer technology. Thus, the OSD module applying the conventional block transfer technology cannot be flexibly applied to the occasion such as the low-level OSD device, in which the pixel data quantity of one pixel is smaller than 8 bits, so that the conventional memory block transfer technology has the poor flexibility of application.